Electronic control modules ("ECMs"), also known as electronic computer control devices, are electronic modules that control the performance of an automobile's engine in response to various conditions input from sensors in the engine and other parts of the automobile. The ECM plugs into an electrical connector, through which it receives inputs from ECM sensors and through which it drives ECM loads, such as lamps, motors, solenoids or other switching devices. The ECM loads are driven by output transistors in the ECM. The output transistors of some ECMs can be damaged if connected to a load having a resistance below that specified by the automobile's manufacturer. For ease of discussion, the term "shorted load" will be used hereafter to include any load resistance below the manufacturer's specification for that load. Unfortunately, the existence of a shorted load is often discovered only when a second ECM is damaged in the course of troubleshooting a first ECM.
Traditionally, mechanics could troubleshoot defective ECMs by using expensive testing equipment supplied by the automobile's manufacturer or by plugging in a replacement ECM and risking damage to the replacement. Further, manufacturer supplied test equipment typically could not be used to service products of other manufacturers. Moreover, such prior art techniques typically involved the use of an ohmmeter, thus necessitating a relatively skilled operator.
It is therefore desirable to provide an automotive electronic circuit analyzer that provides a visual indication of shorted ECM loads, generates minimal electrical noise and consumes minimal power. It is further desirable to provide adaptor means to adapt such an automotive electronic circuit analyzer to a variety of ECMs.